Crotchets of Arenicola 



53 



of A. marina and pusilla in the form of their post- rostral 

 region. 



A. loveni. Crotchets of large examples only, exhibiting late 

 growth-characters, are available (Fig. 27, A from the type specimen 

 and B from a similar specimen 

 collected in Saldanha Bay). They 

 are intermediate in their characters 

 between those of A. marina and \"^ 



cristata, but are, on the whole, f \ 111 



rather nearer those of the latter 

 species. 



A. ecaudata and branchialis. 

 The crotchets of these two species 

 are practically identical in size 

 and form. They do not attain so 

 great a size as the crotchets of the 

 caudate species ; for they appear 

 not to exceed *4 mm. in length, 

 whereas in large examples of 

 A. loveni the crotchets attain a 

 length of '8 mm., in A. marina 

 and cristata *9 mm., and in A. 

 assimilis and pusilla 1 1 mm. 



A crotchet from a post-larval 

 A. ecaudata, 8 mm. long, is shown 

 in Fig. 28, and presents the usual 

 characters found in small crotchets. 

 Fig. 29 represents two crotchets 



from the same 



neuropodium of an 



adult A. ecaudata 



200 mm. long. 



There were in this 



neuropodium 120 



crotchets, of which 



the small one was 



the most dorsal and 

 was about to be cast out, while the large one was just coming 

 into use at the ventral end of the series. There is not usually so much 

 difference in size between the extreme crotchets in the neuropodia of 

 A. branchialis. The rostrum of the crotchets of both these species 



Fig. 25. A. cristata. 

 First crotchet of a 

 larva '25 mm. long. 



Fig. 24. A. pusilla. A, Crotchet from a Nea- 

 politan specimen, 17 mm. long ; B, From the 

 type specimen ; C, From a large specimen, 

 160 mm. long, from Unalaska. 



